Thin film EL device

ABSTRACT

A thin film EL device having high electroluminescent efficiency, a low operating voltage, and a long lifetime. A thin film EL device of the present invention uses, as a luminescent layer, a charge-transport luminescent material that has, within a molecule, a portion contributing to charge transport and a portion contributing to luminescence where at least two molecular orbitals contributing to luminescent transition are localized.

This application is a continuation of U.S. application Ser. No.09/913,644, filed Aug. 17, 2001, now U.S. Pat. No. 6,682,832, which is a371 of PCT/JP00/09064, filed Dec. 20, 2000.

TECHNICAL FIELD

The present invention relates to thin film EL (electroluminescent)devices and to self-luminous devices that can be used as various kindsof light sources for, for example, self-luminous flat panel displays,telecommunications, lighting, and other applications.

BACKGROUND ART

In recent years, LCD panels have been widely used for flat paneldisplays. However, such panels still have several drawbacks such as slowresponse time and narrow viewing angle. In addition, even in many newsystems in which these drawbacks are redressed, there still remainseveral problems, including unsatisfactory performance and increasingcosts in the manufacturing of panels. In these circumstances, thin filmEL devices are attracting attention as new light-emitting devices thathave excellent visibility because of self-luminosity, high-speedresponse, and widespread applicability. In particular, organic ELdevices, thin film EL devices that use, in all or part of the layers,organic materials, allowing for a simple film-forming step such as vapordeposition or coating at room temperature, have been the focus of muchresearch, as these devices are attractive in terms of manufacturing costas well as the above-mentioned characteristics.

In thin film EL devices (organic EL devices), the light emission arisesfrom the recombination of electrons and holes injected from electrodes.Research on such devices has long been conducted; however, since theelectroluminescent efficiency of these devices was generally low, theirpractical applications for light emitting devices was still a long wayoff.

In the meantime, a device was proposed by Tang et al. in 1987 (C. W Tangand S. A. Vanslyke, Appl. Phys. Lett., 51, 1987, pp. 913.) comprising ahole-injecting electrode (anode), a hole-transporting layer, aluminescent layer, and an electron-injecting electrode (cathode) on atransparent substrate wherein ITO (Indium Tin Oxide) was employed as theanode, a 75-nm-thick layer of diamine derivative as thehole-transporting layer, a 60-nm-thick layer of aluminum quinolinecomplex as the luminescent layer, and an MgAg alloy havingelectron-injection properties and stability as the cathode. This devicenot only made improvement in the cathode but also formed a thin filmwhich had satisfactory transparency even with a film thickness of 75 nmand which was uniform and free from pinholes and the like by employing adiamine derivative, having excellent transparency, for thehole-transporting layer. Thus, because reduction in the device's totalfilm thickness became possible, light emission having high luminancewith relatively low voltages could be achieved. Specifically, with a lowvoltage of 10 V or less the device achieved a high luminance of 1000cd/m² or more and a high efficiency of 1.5 lm/W or higher. This reportled by Tang et al. spurred further investigation into improvements incathodes, suggestions on device constructions, and so forth, and thisactive investigation has continued to the present.

Thin film EL devices, generally investigated today, are outlined below.

In addition to a thin film EL device, such as one described in theabove-mentioned report, having a laminate structure of an anode, ahole-transport layer, a luminescent layer, and a cathode formed on atransparent substrate, a device may comprise a hole-injecting layerformed between an anode and a hole-transport layer, may comprise anelectron-transport layer formed between a luminescent layer and acathode, or may comprise an electron-injecting layer formed between theelectron-transport layer and the cathode. Thus, by assigning functionsto each individual layer separately, it becomes possible to selectsuitable materials for each layer, resulting in improvement in devicecharacteristics.

For the transparent substrate, a glass substrate such as Corning 1737 iswidely used. A substrate thickness of about 0.7 mm is convenient for usein terms of its strength and weight.

For the anode, a transparent electrode such as an ITO-sputtered film, anelectron-beam evaporated film, or an ion-plated film is used. The filmthickness is determined by the sheet resistance and visible lighttransmittance required; however, since thin film EL devices haverelatively high operating current densities, in most cases, the filmthicknesses are made to be 100 nm or more so as to reduce the sheetresistances.

For the cathode, an alloy of a low work function metal with a lowelectron injection barrier and a relatively high work function, stablemetal, such as an MgAg alloy proposed by Tang et al. or an AlLi alloy,is used.

For the layers sandwiched between the anode and the cathode, manydevices have a laminate structure, for example, of a hole-transportlayer formed to a thickness of about 80 nm by vacuum vapor deposition ofa diamine derivative (Q1-G-Q2 structure) used by Tang et al. such asN,N′-bis (3-methylphenyl)-N,N′-diphenylbenzidine (TPD) or N,N′-bis(α-naphthyl) -N,N′-diphenylbenzidine (NPD) and a luminescent layerformed to a thickness of about 40 nm by vacuum vapor deposition of anelectron-transport luminescent material such as tris(8-quinolinolato)aluminum. In this structure, in order to increase luminance, generally,a luminescent layer is doped with a luminescent dye.

In addition, in view of the general difficulty in obtaining an organiccompound having excellent electron-transport properties such as onedescribed above, it has also been suggested that in the luminescentlayer/electron-transport layer structure and in the hole-transportlayer/luminescent layer/electron-transport layer structure ahole-transport luminescent material be used for the luminescent layer.

For example, Japanese Unexamined Patent Publication No. 2-250292discloses a device having the hole-transport luminescentlayer/electron-transport layer structure that uses, as thehole-transport luminescent material,[4-{2-(naphthalene-1-yl)vinyl}phenyl]bis(4-methoxyphenyl)amine or[4-(2,2-diphenylvinyl)phenyl]bis(4-methoxyphenyl) amine.

International Patent Publication No. WO96/22273 discloses a devicehaving the hole-transport layer/hole-transport luminescentlayer/electron-transport layer structure that uses, as thehole-transport luminescent material,4,4′-bis(2,2-diphenyl-1-vinyl)-1,1′-biphenyl.

At the 1998 MRS Spring Meeting, Symposium G2.1, the hole-injectinglayer/hole-transport luminescent layer/hole blockinglayer/electron-transport layer structure that uses NPD as thehole-transport luminescent material was disclosed.

Further, Japanese Unexamined Patent Publications No. 10-72580 and No.11-74079 also disclose various hole-transport luminescent materials.

Thus, using a hole-transport luminescent material as well as anelectron-transport luminescent material as the luminescent materialallows for the design of a wide range of materials, which in turnprovides various luminous colors. However, in terms ofelectroluminescent efficiency, lifetimes, and so forth, it cannot besaid that expectations have been met.

When devices are used in the passive-matrix line-at-a-time scanningdisplays, in particular, in order to attain a prescribed averageluminance, peak luminance needs to be increased to very high levels.This increases the operating voltage, causing the problem of increasingpower consumption as a result of power loss or the like caused by wiringresistance. Further, other problems arise, such as an increase in thecost for drive circuits and a decrease in reliability. Furthermore,devices tend to have shorter lifetimes as compared to ones used underconditions of continuous light-emission.

In addition, even with devices having high electroluminescent efficiencyand relatively low operating voltages at direct current operation, whenthe duty ratio increases during operation, the operating voltagerequired to attain a prescribed average luminance is rapidly increasedand also the electroluminescent efficiency itself is reduced as theoperating voltage increases.

Moreover, the above-mentioned[4-{2-(naphthalene-1-yl)vinyl}phenyl]bis(4-methoxyphenyl)amine and[4-(2,2-diphenylvinyl)phenyl]bis(4-methoxyphenyl)amine, disclosed inJapanese Unexamined Patent Publication No. 2-250292, have relativelygood hole-transport properties and high fluorescent yield. However,since both compounds are low-molecular-weight compounds, they sufferfrom the problems of low heat-resistance and particularly a shortlifetime. In addition, because the compounds require luminescent dyedoping, there is a problem concerning manufacturing.

The above-mentioned 4,4′-bis(2,2-diphenyl-1-vinyl)-1,1′-biphenyl,disclosed in International Patent Publication No. WO96/22273, issomewhat superior in terms of heat-resistance as compared to theabove-mentioned compounds. However, since the structure of the compoundis completely symmetric, the molecules easily become associated witheach other, reducing electroluminescent efficiency due to microscopiccrystallization and aggregation. Because of this, devices using thiskind of compound are unable to obtain satisfactory lifetime when usedunder conditions of continuous light-emission. In addition, since thecompound requires luminescent dye doping, there is a problem concerningmanufacturing.

For the above-mentioned Q1-G-Q2 type compound, such as one disclosed inthe 1998 MRS Spring Meeting, Symposium G2.1, besides TPD and NPD, thetrimers of and the tetramers of triphenylamine have also been reported.As for their heat resistance, it has been reported that they havesufficient levels of heat resistance. However, since these compoundsalso have high molecular symmetry, the molecules easily becomeassociated with each other, reducing electroluminescent efficiency dueto microscopic crystallization and aggregation. Because of this, herealso, devices using this kind of compound are unable to obtainsatisfactory lifetimes under continuous use. Particularly when thedevices are operated at high duty cycles, difficulties arise inachieving satisfactory electroluminescent efficiency and low operatingvoltages. In addition, since the compounds require luminescent dyedoping, there is a problem concerning manufacturing.

Devices using the above-mentioned hole-transport luminescent materialsdisclosed in Japanese Unexamined Patent Publications No. 10-72580 andNo. 11-74079 do not require luminescent dye doping, and thus areadvantageous with regard to manufacturing. However, the devices have notyet achieved satisfactory electroluminescent efficiency.

DISCLOSURE OF THE INVENTION

In view of the foregoing and other problems, it is an object of thepresent invention to provide a thin film EL device that achieves highelectroluminescent efficiency, a low operating voltage, and a longlifetime even when the device is operated with direct current or at highduty cycles.

In order to achieve the above-mentioned objects, the present inventorsdesigned materials having various structures and made predictions aboutmore specific properties of the materials by computer simulations.Thereafter, various compounds were actually synthesized and fabricatedinto thin film EL devices. The inventors then obtained experimental dataon the electroluminescent characteristics and lifetimes of the devicesfor both direct current operation and high duty cycle operation. From anenormous amount of these experimental data, the inventors found thatwhen some specific groups of compounds were used as the luminescentmaterial, the devices characteristically achieved extremely highelectroluminescent efficiency, low operating voltages, and exceptionallylong lifetimes over a wide range of operating duty cycles, from a directcurrent to 1/240.

In addition, the molecular orbitals (HOMO and LUMO) of the specificgroups of compounds were observed. The results of the observationsshowed that each individual molecular orbital was localized within amolecule. On the other hand, the hole transporting luminescent materialsdisclosed in Japanese Unexamined Patent Publications No. 10-72580 andNo. 11-74079 were found to have HOMO and LUMO, which are orbitalscontributing to luminescent transition, spreading throughout themolecule. From these data and observations, the present inventors foundthat it is effective in improving in electroluminescent efficiency andso forth when either a hole-transport luminescent material or anelectron-transport luminescent material (collectively referred to as“charge-transport luminescent material”) has at least two molecularorbitals contributing to luminescent transition such that the twoorbitals are localized within a molecule and overlap one another. Thus,the present invention was accomplished.

According to one aspect of the present invention there is provided athin film EL device comprising at least:

a hole-injecting electrode;

an electron-injecting electrode opposed to the hole-injecting electrode;

-   -   and

a luminescent layer sandwiched between the hole-injecting electrode andthe electron-injecting electrode, said luminescent layer containing acharge-transport luminescent material having, within a molecule, aportion contributing to charge transport and a portion contributing toluminescence where at least two molecular orbitals contributing toluminescent transition are localized.

As with the above-mentioned structure, by using a material having aportion contributing to luminescence where at least two molecularorbitals contributing to luminescent transition are localized, becausethe spatial overlap of the molecular orbitals contributing toluminescent transition is large, the energy of a hole-electronrecombination can be utilized more efficiently. Therefore, highelectroluminescent efficiency is achieved. Furthermore, since energyutilization efficiency is high, it is also possible to reduce theoperating voltage and extend the lifetime.

The term “portion contributing to charge transport” is herein defined asa portion which is part of the molecular structure of thecharge-transport luminescent material and which contributes to electrontransport by hopping. One such example is a tetraphenyl phenylenediamineskeleton.

The term “portion contributing to luminescence” is herein defined as aportion which is part of the molecular structure of the charge-transportluminescent material and which includes all molecular orbitalscontributing to luminescent transition. One such example is ananthracene skeleton. It should be noted that this is the portion thatemits light.

The term “molecular orbitals contributing to luminescent transition” isherein defined as orbitals that change the status at light emission, andthe orbitals include at least two orbitals, HOMO and LUMO. It should benoted that the molecular orbitals can be obtained from a calculation ina conventional manner by using, for example, Chem3D available fromCambridgeSoft Corporation, or the MOPAC 97 engine incorporated inWinMOPAC available from Fujitsu Ltd. In addition, each orbital isdefined herein to mean, based on the above calculation results, thesmallest spatial extent covering 90% or more of the probability ofexistence of electrons.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that an electron cloud of the portioncontributing to charge transport and an electron cloud of the portioncontributing to luminescence are localized such that the electron cloudssubstantially do not overlap each other.

As with the above-mentioned structure, when the electron cloud of theportion contributing to charge transport and the electron cloud of theportion contributing to luminescence are localized such that theelectron clouds are substantially separated from each other, the chargetransport properties and the luminescent properties can be exhibitedindividually in different places within a molecule. In addition,quenching due to the interaction between the electron clouds can besuppressed. Consequently, a device is obtained that achieves highelectroluminescent efficiency, a low operating voltage, and an extendedlifetime.

The term “electron cloud of the portion contributing to chargetransport” is defined herein to mean the smallest spatial extentcovering 90% or more of the probability of existence of all theelectrons that are related to charge transport within a molecule.

The “electron cloud of the portion contributing to luminescence” isdefined herein to mean the smallest spatial extent which spatiallyincludes at least two molecular orbitals selected from the molecularorbitals contributing to the above-mentioned luminescent transition andwhich covers 90% or more of the probability of existence of all theelectrons that are related to luminescence within a molecule.

Specifically, the term “being localized such that the electron cloudssubstantially do not overlap each other” herein includes the case wherethere is no overlap between electron clouds that are defined by thespatial extent in which the probability of existence of all theelectrons is 90% but there is overlap between electron clouds in thespatial extent in which the probability of existence of all theelectrons is over 90%. As described above, the electron clouds of eachportion being localized such that the electron clouds do not overlapeach other are advantageous in exhibiting the function; it should benoted, however, that the case where electron clouds are localized suchthat the electron clouds do not overlap each other at all is notrealistic, and thus such a term is used.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the portion contributing to chargetransport and the portion contributing to luminescence are connected bya carbon-carbon bond.

As with the above-mentioned structure, when the portion contributing toluminescence and the portion contributing to charge transport areconnected by a carbon-carbon bond, at least two molecular orbitalscontributing to luminescent transition are localized without spreadingthroughout the molecule, and the electron clouds of each portion arelocalized such that the electron clouds substantially do no overlap eachother. Consequently, a device is obtained capable of exhibiting highcharge transport and luminescent properties.

The term “being connected by a carbon-carbon bond” herein includes notonly a direct single bond between a carbon atom contained in the portioncontributing to luminescence and a carbon atom contained in the portioncontributing to charge transport, but also a bond through a divalentgroup consisting of carbon and hydrogen atoms, such as an alkylene groupand an arylene group. For such a divalent group, one having about 1 to10 carbons is suitable. However, the “carbon-carbon bond” does notinclude a bond through nitrogen atoms or the like, a directcarbon-carbon double bond, and a direct carbon-carbon triple bondbecause these may hinder the localization of molecular orbitals.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the charge-transport luminescentmaterial is a compound having an asymmetric and nonplanar molecularstructure.

As with the above-mentioned structure, when the molecular structure isasymmetric and nonplanar, amorphous characteristics and non-associatingproperties are exhibited, and therefore quenching due to the interactionbetween each of the portions contributing to luminescence of adjacentmolecules or the like can be suppressed. As a result, a device isobtained that has high electroluminescent efficiency.

The term “asymmetric and nonplanar” is defined herein to mean that themolecular structure at its most stable state is not symmetric withrespect to a point, a line, or a plane, but is three dimensional.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the portion contributing toluminescence is present within the luminescent layer at 1×10²⁰ to 1×10²¹per 1 cm³.

As with the above-mentioned structure, when the portion contributing toluminescence is present within the luminescent layer at a specificdensity, a device is obtained that achieves high luminance with highelectroluminescent efficiency. This can be explained by the fact thatwhen the density of the portion contributing to luminescence is too low,sufficient luminance tends not to be obtained; on the contrary, when thedensity is too high, quenching occurs due to the interaction between theportions contributing to luminescence, and thus electroluminescentefficiency tends to be degraded.

Here, the number of the portions contributing to luminescence is countedper portion; for example, when the charge-transport luminescent materialhas two portions contributing to luminescence within a molecule, thenumber of the portions contributing to luminescence per unit area equalsa value that is double the number of molecules per unit area.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the volume ratio of the portioncontributing to luminescence is lower than that of the portioncontributing to charge transport.

As with the above-mentioned structure, when the volume ratio of theportion contributing to luminescence is lower than that of the portioncontributing to charge transport, the possibility of quenching due tothe interaction between the portions contributing to luminescence issuppressed. Consequently, a device is obtained that achieves highelectroluminescent efficiency.

The term “volume ratio” is herein defined as the ratio of the volumeoccupied by the portion contributing to luminescence and the like to thetotal volume of a molecule having the portion contributing toluminescence and the like.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the portion contributing to chargetransport is of a diaryl diphenyl arylenediamine skeleton.

This skeleton is particularly excellent in charge-transport properties,and thus a thin film EL device is obtained that has particularly goodelectroluminescent efficiency and so forth. Above all, a tetraphenylphenylenediamine skeleton, such as a tetraphenyl-p-phenylenediamineskeleton and a tetraphenyl-m-phenylenediamine skeleton, is suitable.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the portion contributing toluminescence is an aryl group containing five or more conjugated bonds.

Such an aryl group has high luminance, and thus a thin film EL device isobtained that has advantages of low operating voltages and so forth.Above all, an anthracene skeleton is suitable.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that an electron-donating substituent isdirectly bonded to the portion contributing to luminescence.

As with the above-mentioned structure, when an electron-donatingsubstituent is directly bonded to the portion contributing toluminescence, the localization of molecular orbitals contributing toluminescent transition is further increased, and thus a device isobtained that achieves higher electroluminescent efficiency.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the charge is a hole.

According to another aspect of the present invention there is provided athin film EL device comprising at least:

a hole-injecting electrode;

an electron-injecting electrode opposed to the hole-injecting electrode;

-   -   and

a luminescent layer sandwiched between the hole-injecting electrode andthe electron-injecting electrode, the luminescent layer containing acompound represented by the following general formula (1):

where Ar1 and Ar2 may be the same or different, and each independentlyrepresents a substituted or unsubstituted aryl group; Ar3 represents asubstituted or unsubstituted arylene group; X represents a substituentcontaining two or more carbon rings and non-planarly bonding to adiphenylamine portion; and Y represents a substituted or unsubstitutedaryl group containing five or more conjugated bonds.

In the above-mentioned compound, the portion contributing to holetransport is of a diaryl diphenyl arylenediamine skeleton and theportion contributing to luminescence includes Y. When a compound havingsuch a molecular structure is used, a device is obtained capable ofexhibiting high hole-transport and luminescent properties. Particularly,when the portion contributing to luminescence is Y (excludingsubstitutes when Y is substituted), at least two molecular orbitalscontributing to luminescent transition are localized, and an electroncloud of the portion contributing to luminescence and an electron cloudof the portion contributing to hole transport are localized such thatthe electron clouds substantially do not overlap each other, and thus asuperior device is obtained. Consequently, a device using theabove-mentioned compound as the hole-transport luminescent materialachieves high electroluminescent efficiency, a low operating voltage,and an extended lifetime.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the compound represented by thegeneral formula (1) has a portion contributing to luminescence where atleast two molecular orbitals contributing to luminescent transition arelocalized.

As with the above-mentioned structure, when at least two molecularorbitals contributing to luminescent transition are localized, becausethe spatial overlap of the molecular orbitals is large, the efficiencyof energy utilization of a hole-electron recombination is increased.Thus, a thin film EL device is obtained that achieves highelectroluminescent efficiency.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the X in the general formula (1) isa substituent represented by the following general formula (2):

where R1 and R2 may be the same or different, and each independentlyrepresents a hydrogen atom or an alkyl group.

As with the above-mentioned structure, when the X in the general formula(1) is a bulky substituent such as one represented by the generalformula (2), this portion becomes twisted and thus the molecules of thehole-transport luminescent material become asymmetric and nonplanar.Thus, molecular association, crystallization, and the like are lesslikely to occur, resulting in a device achieving high electroluminescentefficiency.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the X in the general formula (1) isa substituent represented by the following general formula (3):

where R1 and R2 may be the same or different, and each independentlyrepresents a hydrogen atom or an alkyl group.

The substituent represented by the above-mentioned general formula (3)is a bulky substituent in which a vinyl group is bonded to a substituentrepresented by the above-mentioned formula (2). Thus, molecularassociation, crystallization, and the like are less likely to occur,resulting in a device achieving high electroluminescent efficiency andso forth.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the X in the general formula (1) isa substituent represented by the following general formula (4):

where R1 and R2 may be the same or different, and each independentlyrepresents a hydrogen atom or an alkyl group.

The substituent represented by the above-mentioned general formula (4)is a bulky substituent having nitrogen. Thus, hole-transport propertiescan be improved and the molecules become asymmetric and nonplanar.Therefore, molecular association, crystallization, and the like are lesslikely to occur, resulting in a device achieving high electroluminescentefficiency and so forth.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the X in the general formula (1) isa substituent represented by the following general formula (5):

where R1 and R2 may be the same or different, and each independentlyrepresents a hydrogen atom or an alkyl group.

The substituent represented by the above-mentioned general formula (5)is a bulky substituent having a fluorene skeleton. Thus, the moleculesbecome asymmetric and nonplanar, and therefore molecular association,crystallization, and the like are less likely to occur. Consequently, adevice is obtained that achieves high electroluminescent efficiency andso forth.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the Y in the general formula (1) isan aryl group substituted with an electron-donating substituent.

As with the above-mentioned structure, when Y is substituted with anelectron-donating substituent, the localization of molecular orbitalscontributing to luminescent transition is increased, resulting in adevice achieving higher electroluminescent efficiency.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the Ar3 in the general formula (1)is a p-phenylene group.

As with the above-mentioned structure, when Ar3 is a p-phenylene group,high electroluminescent efficiency is realized and organic synthesis canbe achieved easily, providing a cost advantage.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the Ar3 in the general formula (1)is an m-phenylene group.

As with the above-mentioned structure, when Ar3 is an m-phenylene group,hole-transport properties of the portion contributing to hole transportare improved, resulting in a device achieving high electroluminescentefficiency and a low operating voltage.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the hole-transport luminescentmaterial is a compound represented by the following general formula (6):

where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.

In the above-mentioned compound, the portion contributing to holetransport is of a tetraphenyl-p-phenylenediamine skeleton and theportion contributing to luminescence is an anthryl group. One phenylgroup of diphenylamine is substituted with the above-mentioned anthrylgroup and the other is substituted with a substituted or unsubstituted2,2-diphenylvinyl group. Such compound has a portion contributing toluminescence where at least two molecular orbitals contributing toluminescent transition are localized, and an electron cloud of theportion contributing to luminescence and a molecular cloud of theportion contributing to hole transport are localized such that theelectron cloud and the molecular cloud do not overlap each other.Further, since a bulky substituent, a 2,2-diphenylvinyl group, isbonded, this portion becomes twisted and thus the molecules becomeasymmetric and nonplanar. Thus, a thin film EL device is obtained thatachieves high electroluminescent efficiency, a low operating voltage,and an extended lifetime even when the device is operated at a widerange of operating conditions, from a direct current to high dutycycles.

A compound represented by the above-mentioned general formula (6) may be(4-{[4-(2,2-diphenylvinyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine,(4-{[4-(2,2-diphenylvinyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine,or the like.

In this patent specification, the names of compounds used herein werenamed so as to conform to IUPAC nomenclature rules. Specifically, thecompounds were named using Chemistry 4-D Draw (available fromChemInnovation Software, Inc.) based on the structural formulae for eachcompound.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that a compound represented by thefollowing general formula (7) is used as the hole-transport luminescentmaterial:

where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.

The above-mentioned hole-transport luminescent material includes ananthryl group, corresponding to the portion contributing toluminescence, and a tetraphenyl-p-phenylenediamine skeleton,corresponding to the portion contributing to hole transport, and furtherincludes a bulky substituent, a substituted or unsubstituted4,4-diphenylbuta-1,3-dienyl group. Thus, a thin film EL device isobtained that achieves particularly high electroluminescent efficiency,a low operating voltage, and an extended lifetime even when the deviceis operated at various operating conditions.

A compound represented by the above-mentioned general formula (7) may be(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine,(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine,or the like.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the hole-transport luminescentmaterial is a compound represented by the following general formula (8):

where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.

The above-mentioned hole-transport luminescent material includes ananthryl group, corresponding to the portion contributing toluminescence, and a tetraphenyl-p-phenylenediamine skeleton,corresponding to the portion contributing to hole transport, and furtherincludes a bulky substituent, a substituted or unsubstituted2-aza-2-diphenylaminovinyl group. Thus, a thin film EL device isobtained that achieves particularly high electroluminescent efficiency,a low operating voltage, and an extended lifetime even when the deviceis operated at various operating conditions.

A compound represented by the above-mentioned general formula (8) may be[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}{4-(9-anthryl)phenyl}amino)phenyl]diphenylamine,[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}{4-(10-methoxy(9-anthryl))phenyl}amino)phenyl]diphenylamine,or the like.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the hole-transport luminescentmaterial is a compound represented by the following general formula (9):

where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.

The above-mentioned hole-transport luminescent material includes ananthryl group, corresponding to the portion contributing toluminescence, and a tetraphenyl-p-phenylenediamine skeleton,corresponding to the portion contributing to hole transport, and furtherincludes a bulky substituent, a substituted or unsubstitutedfluorene-9-ylidenmethyl group. Thus, a thin film EL device is obtainedthat achieves particularly high electroluminescent efficiency, a lowoperating voltage, and an extended lifetime even when the device isoperated at various operating conditions.

A compound represented by the above-mentioned general formula (9) may be(4-{[4-(fluorene-9-ylidenmethyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine,(4-{[4-(fluorene-9-ylidenmethyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine, or the like.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the hole-transport luminescentmaterial is a compound represented by the following general formula(10):

where R1, R2, R3, R4, R5, and R6 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and An represents an arylene group composed of two or moresubstituted or unsubstituted fused rings.

The above-mentioned hole-transport luminescent material includes anarylene group composed of two or more fused rings, corresponding to theportion contributing to luminescence, and atetraphenyl-p-phenylenediamine skeleton, corresponding to the portioncontributing to hole transport. In addition, the material includes twobulky substitutes, substituted or unsubstituted 2,2-diphenylvinylgroups. Thus, a thin film EL device is obtained that achievesparticularly high electroluminescent efficiency, a low operatingvoltage, and an extended lifetime even when the device is operated atvarious operating conditions.

A compound represented by the above-mentioned general formula (10) maybe[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}[4-(2,2-diphenylvinyl)phenyl]amino)phenyl]diphenylamine,[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}{4-(2,2-diphenylvinyl)phenyl}amino)phenyl]bis(4-methoxyphenyl)amine,or the like.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the hole-transport luminescentmaterial is a compound represented by the following general formula(11):

where R1, R2, R7, R8, R9, and R10 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and An represents an arylene group composed of two or moresubstituted or unsubstituted fused rings.

The above-mentioned hole-transport luminescent material includes anarylene group composed of two or more fused rings, corresponding to theportion contributing to luminescence, and atetraphenyl-p-phenylenediamine skeleton, corresponding to the portioncontributing to hole transport. In addition, the material includes twobulky substitutes, substituted or unsubstituted fluorene-9-ylidenmethylgroups. Thus, a thin film EL device is obtained that achievesparticularly high electroluminescent efficiency, a low operatingvoltage, and an extended lifetime even when the device is operated atvarious operating conditions.

A compound represented by the above-mentioned general formula (11) maybe[4-({4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenmethyl)phenyl]amino)phenyl]diphenylamine,[4-({4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenmethyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine,or the like.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the hole-transport luminescentmaterial is a compound represented by the following general formula(12):

where R1 and R2 may be the same or different, and each independentlyrepresents a hydrogen atom, an alkyl group, or an alkoxy group; and Anrepresents an arylene group composed of two or more substituted orunsubstituted fused rings.

The above-mentioned hole-transport luminescent material includes anarylene group composed of two or more fused rings, corresponding to theportion contributing to luminescence, and atetraphenyl-p-phenylenediamine skeleton, corresponding to the portioncontributing to hole transport. In addition, the hole-transportluminescent material is substituted with two bulky substitutes,substituted or unsubstituted 4,4-diphenylbuta-1,3-dienyl groups. Thus, athin film EL device is obtained that achieves particularly highelectroluminescent efficiency, a low operating voltage, and an extendedlifetime even when the device is operated at various operatingconditions.

A compound represented by the above-mentioned general formula (12) maybe[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}[4-(4,4-diphenylbuta-1,3-dienyl)phenyl]amino)phenyl]diphenylamine,[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}{4-(4,4-diphenylbuta-1,3-dienyl)phenyl}amino)phenyl]bis(4-methoxyphenyl)amine,or the like.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the hole-transport luminescentmaterial is a compound represented by the following general formula(13):

where R1 and R2 may be the same or different, and each independentlyrepresents a hydrogen atom, an alkyl group, or an alkoxy group; An1 andAn2 may be the same or different, and each independently represents anarylene group composed of two or more substituted or unsubstituted fusedrings; and X1 and X2 may be the same or different, and eachindependently represents a substituted or unsubstituted2,2-diphenylvinyl group, 4,4-diphenylbuta-1,3-dienyl group, orfluorene-9-ylidenmethyl group or a hydrogen atom.

The above-mentioned hole-transport luminescent material includes twoarylene groups composed of two or more fused rings, corresponding to theportion contributing to luminescence, and atetraphenyl-p-phenylenediamine skeleton, corresponding to the portioncontributing to hole transport. In addition, the above-mentioned arylenegroups are substituted with bulky substituents. Thus, a thin film ELdevice is obtained that achieves particularly high electroluminescentefficiency, a low operating voltage, and an extended lifetime even whenthe device is operated at various operating conditions.

A compound represented by the above-mentioned general formula (13) maybe {4-[bis(4-(9-anthryl)phenyl)amino]phenyl}diphenylamine,[4-(bis{4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine,[4-(bis{4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine,[4-(bis{4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine,or the like.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the hole-transport luminescentmaterial is a compound represented by the following general formula(14):

where R4 represents a hydrogen atom, an alkyl group, an alkoxy group, oran aralkyl group; and R1, R2, and R3 may be the same or different, andeach independently represents a hydrogen atom, an alkyl group, or analkoxy group.

The above-mentioned hole-transport luminescent material includes aterphenyl group, corresponding to the portion contributing toluminescence, and a tetraphenyl-p-phenylenediamine skeleton,corresponding to the portion contributing to hole transport. Thismaterial also includes a terphenyl group, which is the portioncontributing to luminescence, and thus a thin film EL device is obtainedthat achieves high electroluminescent efficiency, a low operatingvoltage, and an extended lifetime even when the device is operated atvarious operating conditions.

A compound represented by the above-mentioned general formula (14) maybe [4-(diphenylamino)phenyl][4-(4-phenylphenyl)phenyl]phenylamine,[4-{bis(4-methoxyphenyl)amino}phenyl][4-{4-(4-methoxyphenyl)phenyl}phenyl][4-(1-methyl-1-phenylethyl)phenyl]amine,or the like.

According to another aspect of the present invention the above-mentionedthin film EL device may be such that the hole-transport luminescentmaterial is a compound represented by the following general formula(15):

where R1, R2, R3, and R4 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup.

The above-mentioned hole-transport luminescent material includes twoterphenyl groups, corresponding to the portion contributing toluminescence, and a tetraphenyl-p-phenylenediamine skeleton,corresponding to the portion contributing to hole transport. Thismaterial also includes terphenyl groups, which are the portioncontributing to luminescence, and thus a thin film EL device is obtainedthat achieves particularly high electroluminescent efficiency, a lowoperating voltage, and an extended lifetime even when the device isoperated at various operating conditions.

A compound represented by the above-mentioned general formula (15) maybe [4-(diphenylamino)phenyl][bis{4-(4-phenylphenyl)phenyl}]amine,[4-{bis(4-methoxyphenyl)amino}phenyl]bis[4-{(4-(4-methoxyphenyl)phenyl}phenyl]amine,or the like.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a cross sectional view schematically showing the structure ofa thin film EL device according to a preferred embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawing, a thin film EL device in accordance with apreferred embodiment of the present invention will be described below.FIG. 1 is a cross sectional view schematically showing the structure ofthis thin film EL device.

As shown in FIG. 1, this thin film EL device comprises a hole-injectingelectrode 2, an electron-injecting electrode 6 opposed to theabove-mentioned hole-injecting electrode 2, and a hole-transport layer3, a luminescent layer 4, and an electron-transport layer 5 that aresandwiched between the electrodes, on a substrate 1.

For the substrate 1, there are no particular limitations as long as itis capable of supporting the hole-injecting electrode 2 and so forth,and thus any type of substrate known in the prior art can be used. Itshould be noted, however, that when emitted light is extracted from thesubstrate side, a transparent substrate is used. For a transparentsubstrate, typically, a glass substrate such as Corning 1737 glass isused, but it is also possible to use a resin film such as the one madeof polyester. A preferable thickness of the substrate is 0.5 to 1.0 mmthickness in terms of strength and weight.

For the hole-injecting electrode 2, there are no particular limitationsas long as it functions as the anode and is capable of injecting holesinto the hole-transport layer 3. It should be noted, however, thateither the hole-injecting electrode 2 or the electron-injectingelectrode 6 described below is made to have transparency to extract theemitted light to the outside and it is often the case that normally thehole-injecting electrode 2 is made to be a transparent electrode. Inthis case, an ITO (indium tin oxide) film is usually used. In forming anITO film, in order to ensure a high degree of transparency and a lowresistivity, such film-forming techniques as sputtering, electron beamevaporation, or ion plating are employed. The formed ITO film may begiven various post-treatments to control its resistivity and shape. Thefilm thickness is determined mainly from sheet resistance and visiblelight transmittance; however, since thin film EL devices have relativelyhigh operating current densities, in order to reduce the sheetresistance, films are usually formed to be a thickness of 100 nm ormore, generally 100 to 150 nm. In addition to an ITO film, which is atransparent electrode, it is also possible to use various improvedtransparent conductive layers, such as an In₂O₃—ZnO transparentconductive electrode (IDIXO available from Idemitsu Kosan Co., Ltd.), ora coating film of a transparent conductive coating in which conductivepowder particles are dispersed.

For the electron-injecting electrode 6, an electrode that is composed ofan alloy of a low work function metal with a low electron injectionbarrier and a relatively high work function, stable metal is used; forexample, an MgAg alloy proposed by Tang et al. as described in theBackground Art or an AlLi alloy. In addition, it is possible to usevarious structures of electrodes, such as a multi-layer cathode composedof a Li thin film and an Al film, which is thicker than the Li thinfilm, or a multi-layer cathode composed of a LiF film and an Al film.

The hole-transport layer 3 and the electron-transport layer 5 sandwichedbetween the above-mentioned hole-injecting electrode 2 and theelectron-injecting electrode 6 have no particular limitations, and thusare formed using any type of material known in the prior art. For thehole-transport layer 3, a layer is used composed of a material havinghole-transport properties, such as TPD or NPD described above. It isalso possible to use a specific material-blended type hole-transportlayer, which is disclosed in Japanese Unexamined Patent Publication No.11-260559. For the electron-transport layer 5, a layer composed ofvarious materials having electron-transport properties is used; forexample, an aluminum quinoline complex, such as the above-mentionedtris(8-quinolinolato)aluminum (Alq3), or various compounds, such as allkinds of oxadiazole derivatives or phenanthroline derivatives, can bewidely used.

Next, for the luminescent layer 4, which is the most significant featureof the present invention, the charge-transport luminescent material isused having a portion contributing to charge transport and a portioncontributing to luminescence where at least two molecular orbitals (forexample, HOMO and LUMO) contributing to luminescent transition arelocalized. The portion contributing to charge transport may be of, forexample, a tetraphenyl phenylenediamine skeleton or the like. With thisskeleton, generally, higher electroluminescent efficiency and longerlifetimes than triphenylamine dimer (TPD and the like), so-calledQ1-G-Q2 structure, are achieved. The portion contributing toluminescence may be of, for example, an anthracene skeleton or the like.With this skeleton, particularly good electroluminescent efficiency andhigh charge-transport properties are achieved, and in addition lowoperating voltages and low power consumption are achieved.

Among the above-mentioned charge-transport luminescent materials, amaterial is particularly suitable in which an electron cloud of theportion contributing to charge transport and an electron cloud of theportion contributing to luminescence are localized such that theelectron clouds substantially do not overlap each other. When this kindof material is used, charge transport properties and luminescentproperties can be exhibited separately, and thus an excellent thin filmEL device is obtained. In addition, when a carbon atom of the portioncontributing to charge transport and a carbon atom of the portioncontributing to luminescence are connected by a carbon-carbon bond, theelectron clouds are localized individually such that the electron cloudssubstantially do not overlap each other, ensuring an excellent thin filmEL device.

The luminescent layer 4 is formed using such charge-transportluminescent materials by various film-forming techniques such as vapordeposition. Since the luminescent layer 4 of the present inventionachieves high electroluminescent efficiency, normally, it is notnecessary to dope the layer with luminescent dyes. Thus, a thin film ELdevice suitable for mass production is obtained.

A hole-transport luminescent material may be a compound that isrepresented by the above-mentioned general formula (1). Above all, acompound represented by the above-mentioned general formulae (6) to (15)is preferable, and a compound represented by the general formulae (6) to(13) is more preferable.

For substituted or unsubstituted aryl groups represented by Ar1 and Ar2in the above-mentioned formula (1), preferable examples thereof includethe following: for an unsubstituted aryl group, one having 6 to 20carbons is suitably used. Specifically, a phenyl group, a biphenylgroup, a terphenyl group, a naphthyl group, an anthryl group, aphenanthryl group, a fluorenyl group, and the like, are suitable. Asubstituted aryl group may be one in which the above-mentionedunsubstituted aryl group is substituted with, for example, an alkylgroup having 1 to 10 carbons, an alkoxy group having 1 to 10 carbons, orthe like.

For a substituted or unsubstituted arylene group represented by Ar3 inFormula (1), preferable examples thereof include the following: for anunsubstituted arylene group, one having 6 to 20 carbons is suitablyused. Specifically, a phenylene group, a biphenylene group, aterphenylene group, a naphthylene group, an anthrylene group, aphenanthrylene group, a fluorenylene group, and the like, are suitable.A substituted arylene group may be one in which the above-mentionedunsubstituted arylene group is substituted with, for example, an alkylgroup having 1 to 10 carbons, an alkoxy group having 1 to 10 carbons, orthe like. Among these aryl groups, a substituted or unsubstitutedphenylene group is particularly suitable. A p-phenylene group providesan advantage which allows easy organic synthesis, and an m-phenylenegroup is advantageous because of its hole-transport properties and soforth.

For a substituent represented by X in Formula (1), one having 12 to 30carbons is suitably used. Specifically, a substituent represented by theabove-mentioned formula (2) is suitable.

A substituent represented by Y in Formula (1) is a substituted orunsubstituted aryl group having five or more conjugated bonds.Preferable examples thereof include the following: for an unsubstitutedaryl group, an anthryl group or the like is suitably used. The number ofconjugated bonds is suitably about 5 to 30. For a substituted arylgroup, one in which an electron-donating substituent, such as an alkoxygroup having 1 to 10 carbons, is directly bonded to an unsubstitutedaryl group is suitable.

Further, for each alkyl group in the above-mentioned formulae, onehaving 1 to 10 carbons is suitably used. Specifically, a methyl group,an ethyl group, a propyl group, an isopropyl group, a butyl group, as-butyl group, an isobutyl group, a t-butyl group, and the like aresuitable.

For each alkoxy group in the above-mentioned formulae, one having 1 to10 carbons is suitably used. Specifically, a methoxy group, an ethoxygroup, a propoxy group, a butoxy group, a t-butoxy group, and the likeare suitable.

Each electron-donating substituent in the above-mentioned formulae hasno particular limitations, but an alkoxy group having 1 to 10 carbons,such as a methoxy group or an ethoxy group, is suitably used.

For each arylene group formed by the condensation of two or moresubstituted or unsubstituted rings in the above-mentioned formulae,preferable examples thereof include the following: for an unsubstitutedarylene group, one having 10 to 20 carbons is suitably used.Specifically, a naphthylene group, an anthrylene group, a phenanthrylenegroup, and the like are suitable.

For each aralkyl group in the above-mentioned formulae, one having 7 to20 carbons is suitably used. Specifically, a 1-methyl-1-phenylethylgroup and the like are suitable.

Specific examples of a hole-transport luminescent material representedby the above-mentioned general formulae (6) to (15) are those describedabove.

(Miscellaneous)

In the foregoing, one type of a thin film EL device was explained havingthe hole-transport/luminescent/electron-transport layers sandwichedbetween the hole-injecting electrode and the electron-injectingelectrode; however, the present invention is not limited to thisspecific type of the device. For example, an additional layer, such as ahole-injecting layer, may be provided in the device, or thehole-transport layer and/or the electron-transport layer may be omitted.For the hole-injecting layer, in order to smoothen the surface roughnessof ITO, to attain low operating voltages by improving hole injectingefficiency, to extend lifetimes, and so forth, it is possible to usestar-burst-amine (for example, Japanese Unexamined Patent PublicationNo. 3-308688), oligoamine for example, International Patent PublicationNo. WO96/22273), or the like.

The present invention is explained in more detail below according to thespecific examples. It is to be understood, however, that the presentinvention is not limited to these specific examples. It should be notedthat for each hole-transport luminescent material, one that issynthesized in a conventional manner and sufficiently purified was used,except where specific synthesis examples are noted.

EXAMPLE 1

First, as a substrate having a hole-injecting electrode thereon, acommercially available ITO-coated glass substrate (available from SanyoVacuum Industries, Co., Ltd., size: 100 mm×100 mm×t=0.7 mm, a sheetresistance of about 14 Ω/□) was used, and the substrate was patterned byphotolithography such that the light-emission area is 1.4 mm×1.4 mm withthe overlap of the hole-injecting electrode and an electron-injectingelectrode. After the photolithography, the substrate was given atreatment as follows. The substrate was immersed in a commerciallyavailable resist stripper (a mixture of dimethyl sulfoxide andN-methyl-2-pyrrolidone) to remove the resist, then rinsed with acetone,and further immersed in fuming nitric acid for one minute to completelyremove the resist. The ITO surfaces were cleaned by mechanically rubbingboth (the top and bottom) surfaces of the substrate with a nylon brushas adequately supplying a 0.238% tetramethyl ammonium hydroxidesolution. The surfaces were then rinsed with pure water, followed by aspin dry. Thereafter, the surfaces were given oxygen plasma treatment ina commercially available plasma reactor (Model PR41, available fromYamato Scientific Co., Ltd.) for one minute at an oxygen flow rate of 20sccm, a pressure of 0.2 Torr (1 Torr=133.322 Pa), and a high frequencyoutput of 300 W.

The hole-injecting electrode-coated substrate thus prepared was placedin the vacuum chamber of a vacuum evaporator. The vacuum evaporator usedhere is one in which a main pumping system of a commercially availablevacuum evaporator (Model EBV-6DA, available from ULVAC Japan, Ltd.) ismodified. In this system, the main pumping system is a turbo molecularpump with a pumping speed of 1500 liters/min (TC1500, available fromOsaka Vacuum, Ltd.) and has an ultimate vacuum of about 1×10⁻⁶ Torr orless, and all vapor depositions were carried out in the range of 2 to3×10⁻⁶ Torr. In addition, all vapor depositions were carried out byconnecting a tungsten boat for resistance-heated evaporation to the DCpower supply (PAK10-70A, available from Kikusui ElectronicsCorporation).

The hole-injecting electrode-coated substrate was placed in the vacuumchamber of a system such as one described above. Onto the substrate,N,N′-bis (4′-diphenylamino-4-biphenylyl)-N,N′-diphenylbenzidine (TPT,available from Hodogaya Chemical Co., Ltd.) and4-N,N-diphenylamino-α-phenylstilbene (PS) were co-deposited atdeposition rates of 0.3 μm/s) and 0.01 (nm/s), respectively, to form amaterial-blended type hole-transport layer with a thickness of about 80(nm). Then,(4-{[4-(2,2-diphenylvinyl)phenyl](4-(9-anthryl)phenyl)amino}phenyl)diphenylamine(hereafter referred to as “PPDA-PS-A”), which is a hole-transportluminescent material, was vapor deposited at a deposition rate of 0.3nm/s to form a hole-transport luminescent layer with a thickness ofabout 40 nm.

Here, the PPDA-PS-A was a compound represented by the following chemicalformula (16) and was obtained by synthesizing as follows.

As a starting material, N-acetyl-1,4-phenylenediamine (TCI Catalog No.A0106, 2250 yen/25 g) was prepared and underwent the Ullmann reactionwith iodobenzene. The resulting substance was then hydrolyzed, andfurther underwent the Ullmann reaction with 9-(4-iodophenyl)anthracene.

Thereafter, the resultant was formylated by the Vilsmeier reaction asshown in the following reaction formula (17). Here, for a solvent usedfor the reaction, it is possible to use DMF to obtain high reactivity,but in order to enhance reaction selectivity and increase the proportionof the target compound, N-methylformanilide was used. In addition, sincethe Vilsmeier reaction is electrophilic addition, a carbon having thehighest HOMO electron density became a reactive site, and thus the paraposition of the benzene ring, which is directly bonded to the nitrogen,was formylated. After the formylation, the resultant was thoroughlyisolated by column chromatography and thus the target compound wasextracted.

Then, diethyl diphenylmethyl phosphate, obtained fromdiphenylbromomethane and ethylphosphate, was distilled under reducedpressure and used in the final reaction, and then the portion formylatedas described above was reacted with a diphenylvinyl group. A compoundthus obtained was further isolated thoroughly by column chromatography,and then further sublimed and purified sufficiently.

It should be noted that the foregoing synthesis example shows thatfirst, the skeleton was obtained by the Ullmann reaction, becausegenerally a vinyl bond is thought to be not resistant to hightemperature of the Ullmann reaction, and then the resultant wasformylated by the Vilsmeier reaction, and finally a diphenylvinyl groupwas added; however, it has been confirmed that a synthesis with higheryields is achieved when the coupling of an anthracene portion is carriedout rather at the end by effectively using Pd catalysts and so forth.

Next, onto the so-formed luminescent layer,tris(8-quinolinolato)aluminum (Alq3, available from DojindoLaboratories) was vapor deposited at a deposition rate of 0.3 nm/s toform an electron-transport layer with a thickness of about 20 nm.

Then, only Li from an Al—Li alloy (available from Kojundo ChemicalLaboratory Co., Ltd., the weight ratio of Al to Li is 99:1) was vapordeposited at low temperatures and at a deposition rate of about 0.1 nm/sto form an Li layer with a thickness of about 1 nm. Subsequently, thetemperature of the Al—Li alloy was further increased and when Li wascompletely extracted, only Al was vapor deposited at a deposition rateof about 1.5 nm/s to form an Al layer with a thickness of about 100 nm.Thus, a multi-layer cathode was formed.

To the thin film EL device thus fabricated, after dry nitrogen wasleaked inside the vapor deposition chamber, a Corning 7059 glass lid wasattached with an adhesive (Super Back Seal 953-7000, available fromAnelva Corporation) under a dry nitrogen atmosphere. Thus, a sample wasobtained.

A sample of a thin film EL device thus obtained was evaluated asfollows.

(Evaluation of the Device When Operated with DC Constant-Current)

In order to evaluate the electroluminescent efficiency (cd/A) and theoperating voltage (V), 12 hours after the glass lid was attached to thedevice, the device was operated with DC constant-current under normallaboratory conditions with ambient temperature and humidity. It shouldbe noted that the operating voltage was such a level obtained at aluminance level of 1000 (cd/m²).

As for the lifetime, under the same conditions as described above, acontinuous light-emission test was conducted by operating the device ata DC constant-current level that provides an initial luminance of 1000(cd/m²). Then, the lifetime, which is defined as the time taken forluminance to decrease by half (500 cd/m²), was evaluated.

Here, the device was operated with DC constant-current by using a DCconstant-current power supply (Multi-Channel Current Voltage ControllerTR6163, available from Advantest Corporation). The luminance wasmeasured using a luminance meter (Topcon luminescence meter BM-8,available from Topcon Corporation).

(Evaluation of the Device When Operated with Pulsed Constant-current)

The electroluminescent efficiency (cd/A) and the operating voltage (V)were evaluated by, under the same conditions as described above,operating the device with pulsed constant-current. It should be notedthat the operating voltage was such a level obtained at an averageluminance of 270 (cd/m²).

As for the lifetime, under the same conditions as described above, acontinuous light-emission test was conducted by operating the device ata pulsed constant-current level that provides an average luminance of270 (cd/m²). Then, the lifetime, which is defined as the time taken forluminance to decrease by half (135 cd/m²), was evaluated.

Here, the device was operated with pulsed constant-current by using apulsed constant-current drive circuit. Operating conditions were suchthat the pulse frequency was 100 Hz (10 ms), the duty ratio was 1/240 (apulse width of 42 μs), and the pulse waveform was a square wave. Underthese operating conditions, evaluations were made by operating thedevice at various pulsed current levels. The luminance was measuredusing a luminance meter (Topcon luminescence meter BM-8, available fromTopcon Corporation).

In addition to the above evaluations, the quality of luminescent images,such as uneven luminance and dark spots (non-light-emitting portions),was observed while the device was being operated to emit light by usingan optical microscope with 50 times magnification.

The results of these evaluations are provided in Table 1 to be presentedlater.

EXAMPLE 2

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that(4-{[4-(2,2-diphenylvinyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine(PPDA-PS-AM) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 3

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl](4-(9-anthryl)phenyl)amino}phenyl)diphenylamine(PPDA-PB-A) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

EXAMPLE 4

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl][4-(10-methoxy)(9-anthryl)]pheny}amino)phenyl)diphenylamine(PPDA-PB-AM) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 5

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}(4-(9-anthryl)phenyl)amino)phenyl]diphenylamine(PPDA-PH-A) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

EXAMPLE 6

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}(4-(10-methoxy(9-anthryl))phenyl)amino)phenyl]diphenylamine(PPDA-PH-AM) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 7

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that(4-{[4-(fluorene-9-ylidenmethyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine(PPDA-FM-A) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

EXAMPLE 8

A sample of the thin film EL device was fabricated in a similar manner,to that described in Example 1, except that(4-{[4-(fluorene-9-ylidenmethyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine(PPDA-FM-AM) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 9

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}[4-(2,2-diphenylvinyl)phenyl]amino)phenyl]diphenylamine(PPDA-PS-APS) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 10

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}[4-(2,2-diphenylvinyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine(M2PPDA-PS-APS) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 11

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that4-({4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenmethyl)phenyl]amino)phenyl]diphenylamine(PPDA-FM-AFM) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 12

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-({4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenmethyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine(M2PPDA-FM-AFM) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 13

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}[4-(4,4-diphenylbuta-1,3-dienyl)phenyl]amino)phenyl]diphenylamine(PPDA-PB-APB) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 14

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}[4-(4,4-diphenylbuta-1,3-dienyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine(M2PPDA-PB-APB) was used for the formation of the hole-transportluminescent layer in place of the PPDA-PS-A. The sample was evaluated ina similar manner to that described in Example 1. The results of theevaluations are provided in Table 1 to be presented later.

EXAMPLE 15

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that{4-[(bis(4-(9-anthryl)phenyl)amino]phenyl}diphenylamine (PPDA-A2) wasused for the formation of the hole-transport luminescent layer in placeof the PPDA-PS-A. The sample was evaluated in a similar manner to thatdescribed in Example 1. The results of the evaluations are provided inTable 1 to be presented later.

EXAMPLE 16

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-(bis{4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine(PPDA-APS2) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

EXAMPLE 17

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-(bis{4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine(PPDA-APB2) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

EXAMPLE 18

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-(bis{4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine(PPDA-AFM2) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

EXAMPLE 19

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-(diphenylamino)phenyl][4-(4-phenylphenyl)phenyl]phenylamine (TPPDA)was used for the formation of the hole-transport luminescent layer inplace of the PPDA-PS-A. The sample was evaluated in a similar manner tothat described in Example 1. The results of the evaluations are providedin Table 1 to be presented later.

EXAMPLE 20

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-{bis(4-methoxyphenyl)amino}phenyl][4-{4-(4-methoxyphenyl)phenyl}phenyl][4-(1-methyl-1-phenylethyl)phenyl]amine(MTPPDA) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

EXAMPLE 21

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-(diphenylamino)phenyl][bis{4-(4-phenylphenyl)phenyl}]amine (T2PPDA)was used for the formation of the hole-transport luminescent layer inplace of the PPDA-PS-A The sample was evaluated in a similar manner tothat described in Example 1. The results of the evaluations are providedin Table 1 to be presented later.

EXAMPLE 22

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-{bis(4-methoxyphenyl)amino}phenyl]bis[4-{4-(4-methoxyphenyl)phenyl}phenyl]amine(MT2PPDA) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

Comparative Example 1

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-{2-(naphthalene-1-yl)vinyl}phenyl]bis(4-methoxyphenyl)amine (DANS)was used for the formation of the hole-transport luminescent layer inplace of the PPDA-PS-A. The sample was evaluated in a similar manner tothat described in Example 1. The results of the evaluations are providedin Table 1 to be presented later.

Comparative Example 2

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-(2,2-diphenylvinyl)phenyl]bis(4-methoxyphenyl)amine (MDAPS) was usedfor the formation of the hole-transport luminescent layer in place ofthe PPDA-PS-A. The sample was evaluated in a similar manner to thatdescribed in Example 1. The results of the evaluations are provided inTable 1 to be presented later.

Comparative Example 3

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that4,4′-bis(2,2-diphenyl-1-vinyl)-1,1′-biphenyl (DPVBi) was used for theformation of the hole-transport luminescent layer in place of thePPDA-PS-A. The sample was evaluated in a similar manner to thatdescribed in Example 1. The results of the evaluations are provided inTable 1 to be presented later.

Comparative Example 4

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that instead of forming a40-nm-thick layer of the PPDA-PS-A, which is a hole-transportluminescent material, N,N′-bis (3-methylphenyl)-N,N′-diphenylbenzidine(TPD) was vapor deposited at a deposition rate of 0.3 (nm/s) to form afilm having a thickness of 30 nm, which serves as the hole-transportluminescent layer, and then bathocuproine (BCP, available fromSigma-Aldrich Corporation) was vapor deposited at a deposition rate of0.3 (nm/s) to form a film having a thickness of 5 nm. The sample wasevaluated in a similar manner to that described in Example 1. Theresults of the evaluations are provided in Table 1 to be presentedlater.

Comparative Example 5

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that instead of forming a40-nm-thick layer of the PPDA-PS-A, which is a hole-transportluminescent material, N,N′-bis (α-naphthyl)-N,N′-diphenylbenzidine (NPD)was vapor deposited at a deposition rate of 0.3 (nm/s) to form a filmhaving a thickness of 30 nm, which serves as the hole-transportluminescent layer, and then bathocuproine (BCP, available fromSigma-Aldrich Corporation) was vapor deposited at a deposition rate of0.3 nm/s) to form a film having a thickness of 5 nm. The sample wasevaluated in a similar manner to that described in Example 1. Theresults of the evaluations are provided in Table 1 to be presentedlater.

Comparative Example 6

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-(diphenylamino)phenyl]diphenylamine (TPPDA) was used for theformation of the hole-transport luminescent layer in place of thePPDA-PS-A. The sample was evaluated in a similar manner to thatdescribed in Example 1. The results of the evaluations are provided inTable 1 to be presented later.

Comparative Example 7

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-{(4-phenylphenyl)phenylamino}phenyl](4-phenylphenyl)phenylamine(DPBBPDA) was used for the formation of the hole-transport luminescentlayer in place of the PPDA-PS-A. The sample was evaluated in a similarmanner to that described in Example 1. The results of the evaluationsare provided in Table 1 to be presented later.

Comparative Example 8

A sample of the thin film EL device was fabricated in a similar mannerto that described in Example 1, except that[4-{bis(4-phenylphenyl)amino}phenyl]bis(4-phenylphenyl)amine (TBPDA) wasused for the formation of the hole-transport luminescent layer in placeof the PPDA-PS-A. The sample was evaluated in a similar manner to thatdescribed in Example 1. The results of the evaluations are provided inTable 1 to be presented later.

TABLE 1 Evaluation Result Pulsed DC Constant-Current OperationConstant-Current Operation EL EL Sample Efficiency Driving Life*Efficiency Driving Life* Example Component (cd/A) Voltage (V) (hrs)(cd/A) Voltage (V) (hrs) Others**  1 ITO/TPT +PS(80)/PPDA-PS-A(40)/Alq3(20)/Li/Al 15.4 6.1 3100 15.1 8.2 2500 Good  2ITO/TPT + PS(80)/PPDA-PS-AM(40)/Alq3(20)/Li/Al 16.7 5.9 3300 16.3 8.02600 Good  3 ITO/TPT + PS(80)/PPDA-PB-A(40)/Alq3(20)/Li/Al 15.9 5.8 290015.6 7.8 2400 Good  4 ITO/TPT + PS(80)/PPDA-PB-AM(40)/Alq3(20)/Li/Al17.1 5.8 3000 16.7 7.7 2500 Good  5 ITO/TPT +PS(80)/PPDA-PH-A(40)/Alq3(20)/Li/Al 15.5 5.7 2800 14.9 7.8 2300 Good  6ITO/TPT + PS(80)/PPDA-PH-AM(40)/Alq3(20)/Li/Al 16.4 5.9 2900 16.0 7.92400 Good  7 ITO/TPT + PS(80)/PPDA-FM-A(40)/Alq3(20)/Li/Al 16.1 5.6 330015.7 7.7 2600 Good  8 ITO/TPT + PS(80)/PPDA-FM-AM(40)/Alq3(20)/Li/Al17.2 5.5 3500 16.5 7.4 2800 Good  9 ITO/TPT +PS(80)/PPDA-PS-APS(40)/Alq3(20)/Li/Al 18.8 4.9 3300 18.3 6.9 2700 Good10 ITO/TPT + PS(80)/M2PPDA-PS-APS(40)/Alq3(20)/Li/Al 18.6 5.0 3500 18.17.0 2900 Good 11 ITO/TPT + PS(80)/PPDA-FM-AFM(40)/Alq3(20)/Li/Al 17.95.0 3600 17.2 7.2 3000 Good 12 ITO/TPT +PS(80)/M2PPDA-FM-AFM(40)/Alq3(20)/Li/Al 18.0 4.8 3700 17.2 6.7 3200 Good13 ITO/TPT + PS(80)/PPDA-PB-APB(40)/Alq3(20)/Li/Al 19.0 4.9 3200 18.06.9 2500 Good 14 ITO/TPT + PS(80)/M2PPDA-PB-APB(40)/Alg3(20)/Li/Al 19.25.1 3400 18.6 7.0 2800 Good 15 ITO/TPT +PS(80)/PPDA-A2(40)/Alq3(20)/Li/Al 17.9 5.1 3500 17.1 7.2 2900 Good 16ITO/TPT + PS(80)/PPDA-APS2(40)/Alq3(20)/Li/Al 20.2 4.9 3800 20.0 6.73300 Good 17 ITO/TPT + PS(80)/PPDA-APB2(40)/Alq3(20)/Li/Al 20.1 4.9 360019.3 6.8 3000 Good 18 ITO/TPT + PS(80)/PPDA-AFM2(40)/Alq3(20)/Li/Al 19.84.7 4000 18.9 6.6 3100 Good 19 ITO/TPT + PS(80)/TPPDA(40)/Alq3(20)/Li/Al9.1 7.1 1900 8.3 9.2 1600 Good 20 ITO/TPT +PS(80)/MTPPDA(40)/Alq3(20)/Li/Al 10.0 7.2 2200 9.7 9.2 1800 Good 21ITO/TPT + PS(80)/T2PPDA(40)/Alq3(20)/Li/Al 7.7 7.6 1600 7.5 9.4 1300Good 22 ITO/TPT + PS(80)/MT2PPDA(40)/Alq3(20)/Li/Al 8.6 7.7 1800 8.3 9.61400 Good C1 ITO/TPT + PS(80)/DANS(40)/Alq3(20)/Li/Al 1.5 9.8 170 0.913.8 90 Good C2 ITO/TPT + PS(80)/MDAPS(40)/Alq3(20)/Li/Al 1.8 9.6 1101.2 12.6 50 Good C3 ITO/TPT + PS(80)/DPVBi(40)/Alq3(20)/Li/Al 3.1 8.9300 2.3 12.3 190 Good C4 ITO/TPT + PS(80)/TPD(30)/BCP(5)/Alq3(20)/Li/Al2.1 10.2 180 1.7 15.2 80 Good C5 ITO/TPT +PS(80)/NPD(80)/BCP(5)/Alq3(20)/Li/Al 1.8 10.7 280 1.5 15.7 120 Good C6ITO/TPT + PS(80)/TPPDA(40)/Alq3(20)/Li/Al 1.7 9.7 130 1.1 13.7 70 GoodC7 ITO/TPT + PS(80)/DPBBPDA(40)/Alq3(20)/Li/Al 4.0 9.2 280 2.8 13.2 90Good C8 ITO/TPT + PS(80)/TBPDA(40)/Alq3(20)/Li/Al 3.6 9.4 350 3.2 13.4110 Good C = Comparative EL = Electroluminescent *Life to half luminance**includes uneven luminance, etc.

The results in Table 1 show that according to Examples 1 to 22, thedevices have high electroluminescent efficiency and achieve luminescencewith good visibility with low operating voltages and self-emission. Inaddition, the continuous light-emission tests revealed that the devicesshowed little degradation in luminance, had no defects such as darkspots or uneven luminance, and were capable of operating stably over anextremely long period of time.

Particularly, even in pulsed-operation corresponding to the actual paneloperation, the devices have high electroluminescent efficiency and lowoperating voltages. In addition, the continuous light-emission testsrevealed that the devices showed little degradation in luminance, had nodefects such as dark spots or uneven luminance, and were capable ofoperating stably over an extremely long period of time.

Further, the devices of Examples 1 to 18 achieve higherelectroluminescent efficiency, lower operating voltages, and longerlifetimes as compared to those of Examples 19 to 22. This may beexplained by the fact that in the devices of Example 1 to 18 theelectron clouds of the portions contributing to hole transport and theelectron clouds of the portions contributing to luminescence arelocalized such that the electron clouds substantially do not overlapeach other.

In Table 1 above, the constituent compounds of the devices of eachexample and comparative example are represented in an abbreviated formas follows:

-   TPT indicates    N,N′-bis(4′-diphenylamino-4-biphenylyl)-N,N′-diphenylbenzidine;-   PS indicates 4-N,N-diphenylamino-α-phenylstilbene;-   The PPDA-PS-A indicates    (4-{[4-(2,2-diphenylvinyl)phenyl](4-(9-anthryl)phenyl)amino}phenyl)diphenylamine;-   PPDA-PS-AM indicates    (4-{[4-(2,2-diphenylvinyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine;-   PPDA-PB-A indicates    (4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl](4-(9-anthryl)phenyl)amino}phenyl)diphenylamine;-   PPDA-PB-AM indicates    (4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl][4-(10-methoxy)(9-anthryl)]phenyl}amino)phenyl)diphenylamine;-   PPDA-PH-A indicates    [4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}(4-(9-anthryl)phenyl)amino)phenyl]diphenylamine;-   PPDA-PH-AM indicates    [4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}(4-(10-methoxy(9-anthryl))phenyl)amino)phenyl]diphenylaminine;-   PPDA-FM-A indicates    (4-{[4-(fluorene-9-ylidenemethyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine;-   PPDA-FM-AM indicates    (4-{[4-(fluorene-9-ylidenemethyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine;-   PPDA-PS-APS indicates    [4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}[4-(2,2-diphenylvinyl)phenyl]amino)phenyl]diphenylamine;-   M2PPDA-PS-APS indicates    [4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}[4-(2,2-diphenylvinyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine;-   PPDA-FM-AFM indicates    [4-({4-[10-(fluorene-9-ylidenemethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenemethyl)phenyl]amino)phenyl]diphenylamine;-   M2PPDA-FM-AFM indicates    [4-({4-[10-(fluorene-9-ylidenemethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenemethyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine;-   PPDA-PB-APB indicates    [4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}[4-(4,4-diphenylbuta-1,3-dienylphenyl]amino)phenyl]diphenylamine;-   M2PPDA-PB-APB indicates    [4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}[4-(4,4-diphenylbuta-1,3-dienyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine;-   PPDA-A2 indicates    {4-[bis(4-(9-anthryl)phenyl)amino]phenyl}diphenylamine;-   PPDA-APS2 indicates    [4-(bis{4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine;-   PPDA-APB2 indicates    [4-(bis{4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine;-   PPDA-AFM2 indicates    [4-(bis{4-[10-(fluorene-9-ylidenemethyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine;-   TPPDA indicates    [4-(diphenylamino)phenyl][4-(4-phenylphenyl)phenyl]phenylamine;-   MTPPDA indicates    [4-{bis(4-mthoxyphenyl)amino}phenyl][4-{4-(4-methoxyphenyl)phenyl}phenyl][4-(1-methyl-1-phenylethyl)phenyl]amine;-   T2PPDA indicates    [4-(diphenylamino)phenyl][bis{4-(4-phenylphenyl)phenyl}]amine;-   MT2PPDA indicates    [4-{bis(4-methoxyphenyl)amino}phenyl]bis[4-{4-(4-methoxyphenyl)phenyl}phenyl]amine;-   DANS indicates    [4-{2-(naphthalene-1-yl)vinyl}phenyl]bis(4-methoxyphenyl)amine;-   MDAPS indicates    [4-(2,2-diphenylvinyl)phenyl]bis(4-methoxyphenyl)amine;-   DPVBi indicates 4,4′-bis(2,2-diphenyl-1-vinyl)-1,1′-biphenyl;-   TPD indicates N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine;-   BCP indicates 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline    (bathocuproine);-   NPD indicates N,N′-bis(α-naphthyl)-N,N′-diphenylbenzidine;-   TPPDA indicates [4-(diphenylamino)phenyl]diphenylamine;-   DPBBPDA indicates    [4-{(4-phenylphenyl)phenylamino}phenyl](4-phenylphenyl)phenylamine;-   TBPDA indicates    [4-{bis(4-phenylphenyl)amino}phenyl]bis(4-phenylphenyl)amine;-   Alq3 indicates tris(8-quinolinolato)aluminum;-   Al indicates aluminum; and-   Li indicates lithium.

The laminate structures are described in sequence from the ITO electrodeside using the abbreviations with a slash (/) separating the layers. Thenumbers in parentheses indicate the layer thicknesses in nanometers, andthe plus sign (+) indicates a layer in which two components coexist suchas a doped mixture.

For reference, the absorption wavelengths and oscillator strengths ofcompounds represented by the following chemical formulae (18) and (19)corresponding to a hole-transport luminescent material of the presentinvention and a compound represented by the following chemical formula(20) that does not correspond to a hole-transport luminescent materialof the present invention are provided in Table 2 to be presented later.

TABLE 2 Absorption Wavelength (nm) Oscillator Strength Chemical Formula(18) 343.1 0.466 Chemical Formula (19) 383.3 0.836 Chemical Formula (20)376.8 0.390

Table 2 shows that the compounds represented by the above-mentionedchemical formulae (18) and (19) have higher oscillator strengths thanthe compound represented by the chemical formula (20). The oscillatorstrength and the electroluminescent efficiency are correlated, that isto say, when the oscillator strength is high, the electroluminescentefficiency is high. Thus, a device using the compound represented by thechemical formula (18) or (19) as the luminescent material achieves highelectroluminescent efficiency.

In addition, the compound represented by the chemical formula (19) hashigher oscillator strength than the compound represented by the chemicalformula (18). The compound represented by the chemical formula (19) isone in which a methoxy group (an electron-donating substituent) isdirectly bonded to an anthracene skeleton (a portion contributing toluminescence) of the compound represented by the chemical formula (18).Consequently, a device using a compound, in which an electron-donatingsubstituent is directly bonded to a portion contributing toluminescence, achieves higher electroluminescent efficiency.

Industrial Applicability

As has been described thus far, according to the present invention, athin film EL device uses, as the charge-transport luminescent material,a compound represented by the above-mentioned general formula (1) thathas a portion contributing to charge transport and a portioncontributing to luminescence where at least two molecular orbitalscontributing to luminescent transition are localized. Thus, it ispossible to provide self-luminous devices with excellent visibility thatexhibit high electroluminescent efficiency, low operating voltages, andlonger lifetimes even when operated at various operating voltages. Inaddition, the continuous light-emission tests revealed that the devicesshowed little degradation in luminance and were capable of operatingstably with low power consumption over an extremely long period of time.

Furthermore, even in pulsed operation corresponding to the actualoperation of the passive matrix panel, the devices have low operatingvoltages, high efficiency, and high reliability and are capable ofoperating stably with low power consumption over an extremely longperiod of time.

Thus, the present invention is useful in fields such as various kinds oflight sources used for self-luminous flat panel displays,telecommunications, lighting, and other applications.

1. A thin film EL device comprising at least: a hole-injectingelectrode; an electron-injecting electrode opposed to saidhole-injecting electrode; and a luminescent layer sandwiched betweensaid hole-injecting electrode and said electron-injecting electrode,said luminescent layer containing a compound represented by thefollowing general formula (1):

where Ar1 and Ar2 are the same or different, and each independentlyrepresents a substituted or unsubstituted aryl group; Ar3 represents aphenylene group; X represents a group of the following general formula(2):

where R¹ and R² are the same or different, and each independentlyrepresents a hydrogen atom or an alkyl group; and Y represents asubstituted aryl group having an electron-donating substituent that,prior to substitution with the electron-donating substituent, has fiveor more conjugated bonds.
 2. A thin film EL device according to claim 1,wherein Ar3 represents a p-phenylene group.
 3. A thin film EL deviceaccording to claim 1, wherein Ar3 represents a m-phenylene group.
 4. Athin film EL device comprising at least: a hole-injecting electrode; anelectron-injecting electrode opposed to said hole-injecting electrode;and a luminescent layer sandwiched between said hole-injecting electrodeand said electron-injecting electrode, said luminescent layer containinga compound represented by the following general formula (6):

where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.
 5. A thin film EL device according to claim 4, wherein saidcompound represented by the general formula (6) is(4-{[4-(2,2-diphenylvinyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine.6. A thin film EL device according to claim 4, wherein said compoundrepresented by the general formula (6) is(4-{[4-(2,2-diphenylvinyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine.7. A thin film EL device comprising at least: a hole-injectingelectrode; an electron-injecting electrode opposed to saidhole-injecting electrode; and a luminescent layer sandwiched betweensaid hole-injecting electrode and said electron-injecting electrode,said luminescent layer containing a compound represented by thefollowing general formula (7):

where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.
 8. A thin film EL device according to claim 7, wherein saidcompound represented by the general formula (7) is(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine.9. A thin film EL device according to claim 7, wherein said compoundrepresented by the general formula (7) is(4-{[4-(4,4-diphenylbuta-1,3-dienyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine.10. A thin film EL device comprising at least: a hole-injectingelectrode; an electron-injecting electrode opposed to saidhole-injecting electrode; and a luminescent layer sandwiched betweensaid hole-injecting electrode and said electron-injecting electrode,said luminescent layer containing a compound represented by thefollowing general formula (8):

where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.
 11. A thin film EL device according to claim 10, whereinsaid compound represented by the general formula (8) is[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}{4-(9-anthryl)phenyl}amino)phenyl]diphenylamine.12. A thin film EL device according to claim 10, wherein said compoundrepresented by the general formula (8) is[4-({4-[2-aza-2-(diphenylamino)vinyl]phenyl}{4-(10-methoxy(9-anthryl))phenyl}amino)phenyl]diphenylamine.13. A thin film EL device comprising at least: a hole-injectingelectrode; an electron-injecting electrode opposed to saidhole-injecting electrode; and a luminescent layer sandwiched betweensaid hole-injecting electrode and said electron-injecting electrode,said luminescent layer containing a compound represented by thefollowing general formula (9):

where R4, R5, R6, and R7 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and R1, R2, and R3 may be the same or different, and eachindependently represents a hydrogen atom or an electron-donatingsubstituent.
 14. A thin film EL device according to claim 13, whereinsaid compound represented by the general formula (9) is(4-{[4-(fluorene-9-ylidenmethyl)phenyl][4-(9-anthryl)phenyl]amino}phenyl)diphenylamine.15. A thin film EL device according to claim 13, wherein said compoundrepresented by the general formula (9) is(4-{[4-(fluorene-9-ylidenmethyl)phenyl][4-(10-methoxy(9-anthryl))phenyl]amino}phenyl)diphenylamine.16. A thin film EL device comprising at least: a hole-injectingelectrode; an electron-injecting electrode opposed to saidhole-injecting electrode; and a luminescent layer sandwiched betweensaid hole-injecting electrode and said electron-injecting electrode,said luminescent layer containing a compound represented by thefollowing general formula (10):

where R1, R2, R3, R4, R5, and R6 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and An represents an arylene group composed of two or moresubstituted or unsubstituted fused rings.
 17. A thin film EL deviceaccording to claim 16, wherein said compound represented by the generalformula (10) is[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}[4-(2,2-diphenylvinyl)phenyl]amino)phenyl]diphenylamine.18. A thin film EL device according to claim 16, wherein said compoundrepresented by the general formula (10) is[4-({4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}{4-(2,2-diphenylvinyl)phenyl}amino)phenyl]bis(4-methoxyphenyl)amine.19. A thin film EL device comprising at least: a hole-injectingelectrode; an electron-injecting electrode opposed to saidhole-injecting electrode; and a luminescent layer sandwiched betweensaid hole-injecting electrode and said electron-injecting electrode,said luminescent layer containing a compound represented by thefollowing general formula (11):

where R1, R2, R7, R8, R9, and R10 may be the same or different, and eachindependently represents a hydrogen atom, an alkyl group, or an alkoxygroup; and An represents an arylene group composed of two or moresubstituted or unsubstituted fused rings.
 20. A thin film EL deviceaccording to claim 19, wherein said compound represented by the generalformula (11) is[4-({4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenmethyl)phenyl]amino)phenyl]diphenylamine.21. A thin film EL device according to claim 19, wherein said compoundrepresented by the general formula (11) is[4-({4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}[4-(fluorene-9-ylidenmethyl)phenyl]amino)phenyl]bis(4-methoxyphenyl)amine.22. A thin film EL device comprising at least: a hole-injectingelectrode; an electron-injecting electrode opposed to saidhole-injecting electrode; and a luminescent layer sandwiched betweensaid hole-injecting electrode and said electron-injecting electrode,said luminescent layer containing a compound represented by thefollowing general formula (12):

where R1, to R6 may be the same or different, and each independentlyrepresents a hydrogen atom, an alkyl group, or an alkoxy group; and Anrepresents an arylene group composed of two or more substituted orunsubstituted fused rings.
 23. A thin film EL device according to claim22, wherein said compound represented by the general formula (12) is[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}[4-(4,4-diphenylbuta-1,3-dienyl)phenyl]amino)phenyl]diphenylamine.24. A thin film EL device according to claim 22, wherein said compoundrepresented by the general formula (12) is[4-({4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}{4-(4,4-diphenylbuta-1,3-dienyl)phenyl}amino)phenyl]bis(4-methoxyphenyl)amine.25. A thin film EL device comprising at least: a hole-injectingelectrode; an electron-injecting electrode opposed to saidhole-injecting electrode; and a luminescent layer sandwiched betweensaid hole-injecting electrode and said electron-injecting electrode,said luminescent layer containing a compound represented by thefollowing general formula (13):

where R1, and R2 may be the same or different, and each independentlyrepresents a hydrogen atom, an alkyl group, or an alkoxy group; An1 andAn2 may be the same or different, and each independently represents anarylene group composed of two or more substituted or unsubstituted fusedrings; and X1 and X2 may be the same or different, and eachindependently represents a substituted or unsubstituted2,2-diphenylvinyl group, 4,4-diphenylbuta-1,3-dienyl group, orfluorene-9-ylidenmethyl group.
 26. A thin film EL device according toclaim 25, wherein said compound represented by the general formula (13)is[4-(bis{4-[10-(2,2-diphenylvinyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine.27. A thin film EL device according to claim 25, wherein said compoundrepresented by the general formula (13) is[4-(bis{4-[10-(4,4-diphenylbuta-1,3-dienyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine.28. A thin film EL device according to claim 25, wherein said compoundrepresented by the general formula (13) is[4-(bis{4-[10-(fluorene-9-ylidenmethyl)(9-anthryl)]phenyl}amino)phenyl]diphenylamine.29. A thin film EL device comprising at least: a hole-injectingelectrode; an electron-injecting electrode opposed to saidhole-injecting electrode; and a luminescent layer sandwiched betweensaid hole-injecting electrode and said electron-injecting electrode,said luminescent layer containing a compound represented by thefollowing general formula (14):

where R4 represents a hydrogen atom, an alkyl group, an alkoxy group, oran aralkyl group; and R1, R2, and R3 may be the same or different, andeach independently represents a hydrogen atom, an alkyl group, or analkoxy group.
 30. A thin film EL device according to claim 29, whereinsaid compound represented by the general formula (14) is[4-(diphenylamino)phenyl][4-(4-phenylphenyl)phenyl]phenylamine.
 31. Athin film EL device according to claim 29, wherein said compoundrepresented by the general formula (14) is[4-{bis(4-methoxyphenyl)amino}phenyl][4-{4-(4-methoxyphenyl)phenyl}phenyl][4-(1-methyl-1-phenylethyl)phenyl]amine.